1. Field of the Invention
The present invention relates to a character printer, and more particularly, to a character printer with the ability of preventing the printer from entering into a test mode unintentionally during the usual key operation.
2. Description of the Related Art
For a compact character printer incorporating a test program, it is not desirable to have a special key dedicated to the initiation of the test program. Therefore, conventional printers of this type are designed to enter into the test mode by use of some keys that are commonly used in the normal operation mode. Generally, a rule of key operation for bringing the printer into the test mode is established based on a program so that the printer does not enter into the test mode unintentionally during the usual key operation. However, it is not desirable either to prepare a special program for establishing the test mode setting rule.
There has been proposed a procedure of initiating a test program in such a manner that the power switch is turned on while a specific function key is kept pressed, as described in Japanese Patent Laid-open No. Sho 54-142037. According to this method, the rule of test program initiation can he included in the existing power control program, and it does not necessitate a special program.
However, recent character printers have a growing number of operational functions that necessitate individual test programs. The number of function keys is limited, and it is difficult for the operator to remember and use the function keys correctly to test corresponding functions. Moreover, this method is not capable of allowing only specific operators to run certain test programs.